What the Fire Chief Should Know About Radio
Ignorant Installation—Improper Insulation—Effect of Nearby Heavy Voltages—All Aerials Should Be Inspected—Use by Fire Department
THE subject of the radio as regards its fire hazards is becoming more and more a vital one, as the use of this most modern of conveniences becomes general and the installation of sets by amateurs, who know little of its fire hazards, increases. Professor Brown has treated the subject in the following article from the stand point of the fire hazard.
Electricity is one of the most important and one of the most vital attributes that science has given to the world. Whenever we consider or think of an electrical installation, we think of the fire hazard connected with it. We sometimes wonder if accounting for fires by means of faulty electric wiring is overdone, but that is a problem we cannot decide offhand. It is a truth that electricity and faulty wiring is responsible for a large number of fires.
Radio, as one of the most recent developments in the applications for electricity, is no exception to the general rule of fire risk. The almost undreamed of growth of radio in the last few years has brought it before the public in this respect. So far as the fire risk is concerned, we can divide radio installations into two general classes, sending stations and receiving stations. Regarding the transmitting stations, we can further divide them into two classes from the standpoint of fire hazard, one of these being the spark way of transmitting, and the other the continuous wave. By comparison, the spark transmitter is much more dangerous as a fire hazard than the continuous wave transmitter. There are a number of reasons for this, one is the extremely high potentials in the transmitting circuits. The other reason is due to the surges or so-called kickbacks which take place in these allied circuits. So far as those two conditions are concerned, they are largely the result of faulty installation or faulty insulation.
Hazard of Ignorance in Installation
We must remember in considering transmitting stations, that the majority of them are put up by boys or young men who are ignorant of the amount of insulation which should be provided. They are not versed in what they are handling and they are not versed in the design of their circuit to prevent trouble. Take the first case mentioned of extremely high potentials. There will have to be unusually good insulation, as all insulations will not stand up under all conditions. In these excessive potentials which run up to several hundred thousand volts, and are not properly taken care of in the way of insulation, we naturally have dangerous fire hazard. These always cause potential fire, if the cause of kick-back or surges themselves are produced by surges of transmitting circuit power and are reflected back into the low volt circuits which are used for supply to the transmitter itself.
Danger from Kick-back With Improper Insulation
Suppose, for instance, we are drawing our supply from the lighting circuit, and perhaps through the lighting transformer. The surge in our transmitting circuits will be reflected back through our power transformer into our system, which is well insulated for normal conditions. As a result, there is a breakdown in the insulation, in the wiring itself perhaps, or in fixtures within the house and this furnishes a very likely chance for fire. All that is necessary is to have some inflammable material present and the heat furnished by the kick-back will usually take care of the rest.
“One purpose of inspection and regulation is from the standpoint of fire hazard and the other from the hazard to life. It is only a matter of time until such inspection will have to be universal where inspection of electric wires is at all followed.”
As regards these two risks they can normally be taken care of by proper insulation, proper design in placing circuits, and by proper insulation of these circuits. As was said before, the normal circuit set up is put up by a man who is not familiar with conditions, not knowing how to take care of it, so it is largely the circuits and connecting parts that are defective in the qualities necessary to prevent fires. But in practically all cases, proper insulation will take care of them. In the case of kick-back, it is not so much a case of insulation as it is prevention or protection.
Installation of 2-K. Transformer
One step in protection against kick-back is the installation of a 2-K. transformer between the power supply and the transmitting circuit. In addition to this so-called kick-back, preventers should be supplied to both sides of this transformer. A kick-back preventer normally takes the form of two condensers of the telephone type, each of which will have a capacity in the neighbohood of one-half connected to a condenser across the line and around the middle or common connection. Both sides of the insulating transformer should be supplied with such condensers. In addition to that it is quite necessary and it is customary to connect a similar back over the lamps. Neither of these is to be taken as a cure, they are anything but sure, but they are preventers from the practical standpoint and should be used.
Effect of Undue Voltages in Nearby Circuits
One other risk that is quite possible and pronounced where the spark transmitting station is operating, is the effect of undue voltages in nearby circuits. It is highly improper to have the radio circuits very close to any additional circuits that might be present in the way of telephone or lighting circuits. Also, it is wrong to have any of the circuits parallel for any considerable length on any of these circuits. There is always present the possibility of fire resulting.
Regarding the continuous wave transmitting station, the fire risk produced there is negligible with respect to that produced by the spark station. In the first place the voltages used are considerably lower, but that is not dangerous provided proper protection is taken. Consideration from the high voltages not being present, kick-backs are also eliminated. So then, with proper insulation and insulators, the continuous wave transmitter amounts to a very small item from the standpoint of fire hazard.
Taking the receiving circuits and the execution of the aerial, we have comparatively, if any, risk as regards fire. The potentials used are too low to be of any consequence when the amount of danger is considered, and we can consider the fire risk negligible. It should be borne in mind that in any receiving circuit in any electrical circuit a reasonable precaution should be taken to eliminate as far as possible any chance whatever of fire as a result.
Hazard of Antennas in Electrical Storms
Treating the antennas, we know that whenever we have the antenna system we always have a hazard in case of storm, taking for granted an electrical storm. The question of actual value of that hazard will depend on the location of the aerial itself. Take as two extremes the aerial in the city and comparing this with the aerial in the rural district, the chances are by no means equal. Under city conditions where the aerial is only one conductor perhaps pretty well surrounded by a network of air conductors, such as telephone lines, it is largely protected and does not become a very serious fire hazard. Where we consider the aerial in the rural district where it is one of the very few conductors exposed, we can expect more or less trouble from that source. The aerial becomes in the rural district a real hazard from the standpoint of fire. The aerial of any receiving set, however, whether it be in a city or in the rural districts should always be supplied with an approved form of arrester. This is not only necessary but constitutes a very logical and very valuable first step. In addition to such an arrester, every aerial transmitting station or receiving station in the congested or rural districts should be grounded when not in use through an approved ground switch and ground connection. That is bringing protection so far as the aerial is concerned in limits.
Inspection of Aerials Important
The aerial should not be overlooked as a fire hazard whether in town or out of town. The matter of assurance of protection and proper construction should not be overlooked, especially since the very rapid and phenomenal growth in the radio field has taken place, which will necessarily call for a rather extended inspection. Inspection has been instigated in some centers,—take Cleveland, for example. The inspection not only covers protective devices but actually covers mechanical construction of the aerial itself, that is with regard primarily to other circuits such as power circuits, trolley lines, telephone lines, etc. In the first place if the aerial is properly put up mechanically and electrically, and in case of failure mechanically of the aerial or either one of the other systems there is no other connection between them as a result. One purpose of such inspection and regulation is from the standpoint of fire hazard and the other from the hazard to life. It is only a matter of time until such inspection will have to be universal where inspection of electric wires is at all followed. We will have to keep in mind, of course, all of the conditions in connection with aerial and other radio construction in a time of inspection, and inspect it on that basis. For instance, a man who is installing the radio system perhaps is of limited finances, that is a common condition. Not so much in the up-todate receiving stations, but rather the transmitting stations. A man many times puts it up without sufficient funds to do it correctly, he substitutes this and that thing, and inspection should be made in those cases, and he should be ruled out just the same as the man who is putting in his own electric wiring system.
Radio’s Use By the Fire Department
Aside from thinking of radio as a dangerous piece of equipment to have around, the chances are very good that it will become a convenient help in actual fire-fighting business. That is particularly true, and is coming, I think, to be more and more a reality today especially since the very phenomenal development of the radio telephone. As long as the radio telegraph is practically the only means of communication by radio, the proposition was entirely different from what it is now. But with the telephone and improved equipment of transmitting and receiving, there is no reason to believe why the near future will not bring out perfectly practical transmitting and receiving stations to allow direct communication between headquarters and other places. During time of fire the question comes up, of course, in the matter of interference. This cannot be overlooked but it can be overcome. Largely by assigning in each locality certain wave lengths or territory in which nobody else would be allowed to operate. Within such territory the fire departments will have to operate. There is every reason to believe that such a condition can and will exist. As to activity along that line at the present time we cannot see, it is not more than in the first experimental stages. The police departments have done more along that line for purposes of communication. But even there, it is still in process of development.
(Continued on page 413)
What Chief Should Know About Radio
(Continued from page 398)
Just one word more in regard to the fire risk produced by the spark transmitter. It might be of interest to those who do not otherwise know that the spark transmitter which is the fire hazard in radio, is very rapidly going out of date, on account of the demands of the public in the way of elimination of interference, particularly in broadcasting fields and also from the standpoint of views taken of it by the Department of Commerce under whose control all radio activities are carried on, and through them into the official activities of the radio inspectors themselves. Take our own locality as an example, if I am not mistaken, there are no spark stations in Columbus at the present time. A year ago there were quite a few, but I consider this fire hazard in radio is being eliminated both by influence and by choice.
How far the use of radio for the fire department will go, time alone will tell.
(Excerpts from paper read before the Fire Chiefs’ Club of Ohio at its annual convention in Columbus.)